Synthesis And Properties Of High-efficiency Luminescent Materials Of Coumarin Derivatives

OLED displays have been known as"dream displays".OLED has a variety of attractive features,such as color or white self-emitting,applications in the flat and solid-state devices,fast response speed,light weight and suitability for flexible applications.Therefore,OLED is not only an interesting scientific field,but also has great potential in the main market applications.In this thesis,the high-efficiency luminescent coumarin materials are designed as the electroluminescent guest materials with low synthesis cost and excellent performance,so as to improve the efficiency of OLED devices.The specific research contents are divided into the following three parts:In the first part,three biscoumarin dyes bridged by polycyclic aromatic bridges(anthracen,pyrene and dibenzo[g,p]chrysene)were prepared as the emissive materials for the application of organic light-emitting devices.The relationship between their structures,photophysical properties,electrochemical properties and performances of organic light-emitting devices is described.The multilayered doped devices with a configuration of ITO/NPB(20 nm)/TBADN:biscoumarin compound(x wt%,30 nm)/TPBI(30 nm)/Liq(2 nm)/Al(100 nm)have been successfully fabricated by vacuum-deposition method.All the devices showed green emission with high electroluminescent efficiencies.Especially,the device based on the compound C-Py-C containing pyrene as a bridge group at 7%doping concentration showed the best performance with a maximum brightness of 10552 cd/m~2,maximum luminous efficiency of 5.39 cd/A and maximum external quantum efficiency(EQE)of 2.35%.At the same doping concentration(7 wt%),the maximum brightness of 7796 cd/m~2,maximum luminous efficiencies of 3.24 cd/A and maximum external quantum efficiency of2.17%were observed from the devices based on C-An-C.For the compound C-DBC-C,the devices with 10 wt%doping concentration showed the maximum brightness of 8433 cd/m~2,maximum luminous efficiencies of 5.19 cd/A and maximum external quantum efficiency of2.13%.In comparison with the device performances of the three compounds,the compound C-Py-C exhibited better EL performances than C-An-C and C-DBC-C,which is consistent with their photoluminescence quantum yields.In the second part,three new coumarin derivatives containing aromatic ring imidazole units were synthesized and successfully applied to organic light-emitting devices.Due to the?-conjugated structure of the planar and rigid polyaromatic ring imidazole skeleton,the three compounds BI-C,PI-C and PyI-C all show good thermal stability and strong emissions from greenish-blue light(479 nm)to green light(519 nm)and high photoluminescence quantum efficiency of 94%,97%and 98%in chloroform solution.By vacuum deposition,multilayer doped devices were successfully prepared.Compounds BI-C,PI-C and PyI-C are used as doping materials to make OLED device structures:ITO/TAPC(30 nm)/CBP:Dopant(x wt%,35 nm)/TPBI(30 nm)/Liq(2 nm)/Al(100 nm).Among them,the device of compound BI-C has the best performance at a doping concentration of 6 wt%,the luminous brightness is 984 cd/m~2,the maximum current efficiency is 2.86 cd/A,the maximum power efficiency is 0.91 lm/W,and the maximum external quantum efficiency(EQE)is 1.59%.The device with compound PI-C has the best performance of the light-emitting device at a doping concentration of 12 wt%,the luminous brightness is 2421 cd/m~2,the maximum current efficiency is 6.07 cd/A,and the maximum power efficiency is 4.77 lm/W,the maximum external quantum efficiency(EQE)is 2.78%.The device with 12 wt%doping concentration of compound PyI-C exhibited a maximum brightness is 2598 cd/m~2,and the maximum current efficiency is 4.80 cd/A and the corresponding power efficiency is 1.35 lm/W,and the maximum external quantum efficiency is 2.29%.In the third part,two new coumarin derivatives PXZ-C and PTZ-C containing phenothiazine or phenoxazine structural units were synthesized,and they were analyzed by elemental analysis,NMR and MS Characterization which determined its molecular structure and molecular mass.The photophysical and electrochemical properties and thermal properties of the compounds PXZ-C and PTZ-C were systematically studied by testing their UV-visible absorption spectra,photoluminescence spectra in different solutions and thin film states,cyclic voltammetry,and thermogravimetric analysis.In summary,the results showed that the compounds PXZ-C and PTZ-C have good thermal stability.The compound PTZ-C emits weak blue-green light under the excitation of ultraviolet light,while the compound PXZ-C emits weak blue light.